Television receiver



Dec. 24, 1940. A. A. LINSELL TELEVISION RECEIVER Filed Nov. 27, 1936 1 4 1 1 1 1 1" %Ylr/I- M E INVENTOR AZFREDA. L/MYHZ BY z 7 fia'v-f/l ATTORNEY Patented Dec. 24, 1940 PATENT OFFICE TELEVISION RECEIVER Alfred Aubyn Linsell, Sydenham, London, England, assignor to Radio Corporation of America, a corporation of Delaware 7 Application November 27, 1936, Serial No. 113,025 In Great Britain December 3, 1935 11 Claims.

producer tube must be adjusted when. changing over from one station to another since the scanning line frequencies are different. There is, however, a. second adjustment, not so obvious, which is necessary. when changing over, and mere change of scanning line frequency alone will not produce a satisfactory and useful result. This second adjustment is adjustment of the size of the scanning spot. Given a predetermined, designed picture area at the receiver (this is the position in practice) the size of the scanning spot for the case where there are only 240 lines per picture must be (assuming no overlap between scanning lines) about double that of the scanning spot for the other case where 405 lines per picture are scanned.

According to this invention a television receiver capable of reproducing different television programs transmitted with predetermined different scamii-ng line frequencies comprises means automatically and selectively operated under the control of the scanning line frequency in the television signals being received at any time for selecting that one of a. plurality of sets of predetermined adjustments (each set including at least an adjustment of scanning line frequency and an adjustment of scanning spot size) which is appropriate for reproduction of the pictures transmitted with the said scanning line frequency.

The invention is illustrated in and further explained in connection with the accompanying diagrammatic drawing in which Fig. 1 is a circuit diagram showing one embodiment of my invention, and Figs. 2, 3 and 4 show circuit diagrams showing further modifications of the embodiment of my invention shown in Fig. l.

Although a number of circuitadjustments may be necessary when changing over a cathode ray tube television receiver from a state in which it can reproduce pictures transmitted with one scanning line frequency to a state in which it can reproduce pictures transmitted with another, there are, as already stated, two main adjust ments always required, the first being the obvious adjustment of scanning line frequency and the second being the adjustment of the size of the scanning spot. Consider a normal case (see Fieure 1) where a cathode ray reproducer tube I 5 is provided with a cathode 2 a control electrode 3 and two apertured tubular auxiliary anodes 4, 5, in succession in the path of the electron beam, that which is further from the cathode 2 (namely anode 5) receiving a higher bias potential than 10 the other. In general the bias potentials for the two auxiliary anodes are obtained as shown in Figure 1 from-the same source 6 of potential, the lead to the lower potential anode 4 being connected to 'a tap upon the source. The size of the 15 spot produced by the cathode ray upon the fluorescent screen of the tube will be a function of the relative potential between the two auxiliary anodes 4, 5, and accordingly one change in adjustment which may be made when changing over from reception with one scanning line frequency to reception with anothera change over 'whichinvolve's a change in spot sizeis a change in the potential or potentials applied to one or both the auxiliary anodes. In carrying out the present invention in the embodiment shown in Figure 1 the higher potential auxiliary anode 5 is connected to the positive terminal of the potential source 6 and the lower potential anode 4 is connected to a switch 1 which is automatically operated in manner to be described later which can contact as shown with either of two difi'erent taps upon the said potential source. The taps are such that for one position of the switch the spot size is correct for reception of pictures having one (pre-' determined) scanning line frequency while for 'the other switch position the spot size is correct for reception of pictures having the other (predetermined) scanning line frequency. I,

As regards the question of adjustment of the'40 scanning line deflecting frequency at the receiver, assume that this deflection is obtained electrostatically by mutually perpendicular pairs of plates 9; H), as in the usual way by saw-tooth Waves derived from a synchronized saw-tooth -wavel generator. such as a relaxation oscillator generator or blocking oscillator generator-represented inFigure 1 by a rectangle 8whose operating frequency is determined by the rate of charge (or in some cases of discharge) of a condenser associated with a resistance. Obviously if a single frequency determining condenser be provided and there be two resistances of difierent value adapted to be selectively connected in circuit by means of a suitable switch, then two deflecting line frequencies may be obtained according as to which resistance is in circuit. Therefore, in carrying out the present invention in the embodiment shown in Figure 1 there is provided a switch I4 (also automatically operated in manner to be described later by the same means as are employed to operate switch 'I) connected so that it selects either of two resistances I2 or I3 for connection with the frequency determining condenser II so that either of two scanning line frequencies can be obtained from the generator. As stated the switches I4 and 'I are automatically operated together (the mechanical interconnection between these switches is indicated by a chain line) so that the frequency and scanning spot size selected for one position of the switches are appropriate for giving scanning action at one of the desired scanning line frequencies, and those selected for the other position are appropriate for giving scanning action at the other.

The switches I and I4 are operated automatically in dependence upon the scanning line frequency in the incoming television signals present at any time. One way illustrated in Figure 2 of securing such automatic operation is as follows:

The demodulated or television signal output from the radio receiver proper (represented by the rectangle I5 of Figure 2) of the whole receiving apparatus is fed to two auxiliary circuits IE, IT, one of which is tuned to one and the other to the other of two (predetermined) scan line frequencies for which the receiving apparatus is adapted. (Of course, if the receiver is to be able to receive on more than two scan line frequencies there will be a correspondingly increased number of tuned circuits, a correspondingly increased number of possible (predetermined) adjustments and a correspondingly increased number of switch positionsone for each adjustment.) In order to improve the sharpness or selectivity of these tuned circuits tuning forks or equivalent mechanically resonant devices may be employed: for example, as shown in Figure 2 a coil in each tuned circuit I6, Il may be coupled to an output coil I5 fed from the radio receiver proper with the aid of a tuning fork I8 or I9 in the manner well known per se in tuning fork controlled oscillators. Each tuned circuit is in series with a rectifier 20 or 2I and the rectified outputs are fed differentially to a differential relay system R whose armature 22 may operate mechanically the switches I and I4 of Figure 1 or may be provided with contacts so as in effect to constitute the moving parts of these switches. As shown the relay R in one position connects contacts 23 together and in the other connects contacts 24 together. These contacts may control the switches I, I4, by any known means (not shown). As stated, however, the relay armature 22 may cooperate with suitably disposed contacts so as itself (in conjunction with the said contacts) to constitute the moving parts of the switches I and I4. Thus if one television program is being received the tuned circuit which is responsive to the scan line frequency employed for that program will be predominantly energized and the armature of the differential relay system will accordingly be moved into that position in which it completes the necessary circuits for selecting those predetermined adjustments (scanning spot size and scan line generator frequency adjustments) appropriate to the program being received. When the other program is being received the armature of the differential relay system is moved over into its other position and the other set of adjustments is established.

It is not necessary in carrying out this invention to use electro-mechanical relays. For example, as shown in Figure 3 the necessary changes in auxiliary anode potential (for securing change in scanning spot size) may be obtained by connecting the two auxiliary anodes 4, 5 each to one end of a resistance 26 which is in series with an anode battery in the anode circuit of a thermionic valve 25, the auxiliary anode 5 being connected to the more positive end of the said resistance. The two rectifiers 20, 2|, fed from the two resonant circuits I6, H, are connected to apply their rectified outputs differentially via a centre tapped resistance 25 between grid and cathode of the said valve 25 and the whole arrangement is such that when one program is being received the grid bias on the valve is of one predetermined value While when the other is being received it is of another. Accordingly for these two possible predetermindconditions there will be two possible predetermined values of anode current, and therefore, two possible predetermined values of auxiliary anode potentials.

A similar differentially controlled valve arrangement may be employed for changing over the scan line generator frequency. For example as shown in Figure 4 the frequency controlling condenser I I in the said generator (not shown in Figure 4) may be connected in series with a resistance II and an anode battery in the anode circuit of a thermionic valve 21 whose grid circuit is differentially energized via. a centre tapped I sistance II and the frequency determining condenser I I. The two possible (predetermined) values of grid bias upon this valve 21 will correspond, therefore, with two different (predetermined) values of effective resistance in association with the frequency determining condenser, and therefore, two different values of scan line generator frequency.

Having now described my invention, what I claim is:

1. A television receiver apparatus reproducing different television programs transmitted with different predetermined scanning line frequencies by tracing a spot of light in a line for line manner over a predetermined area comprising thermionic means automatically and selectively operated under the control of the scanning line frequency in the television signals being received at any time for selecting that one of a plurality of sets of predetermined adjustments of scanning line frequency and scanning spot size while maintaining the pattern area traced substantially constant.

2. An apparatus as claimed in claim 1 wherein the automatically and selectively operated means include a plurality of resonant circuits each responsive to a different one of the scanning line frequencies.

3. Apparatus in accordance with claim 1 and wherein picture reproduction is effected by a cathode ray tube of the type having two auxiliary anodes the potentials upon which determine the size of the scanning spot and wherein the predetermined sets of adjustments include adjustments of the relative potentials upon the said two anodes whereby upon the selection of any one set of adjustments, the potentials upon said anodes are selected at the correct values to give the proper size of scanning spot.

4. The steps in the method of operating a television receiver wherein is provided means to receive television signals, a cathode ray tube and ray deflecting means which comprise developing a cathode ray beam adapted to be focused to predetermined cathode ray spot sizes and developing a plurality of predetermined deflecting frequencies, and thermionically selecting one of the predetermined spot sizes and one of the predetermined deflecting frequencies in accordance with the received television signals.

5. The steps in the method of operating a television receiver wherein is provided means to re-,

ceive television signals, a cathode ray tube and ray deflecting means which comprise developing a cathode ray beam adapted to be focused to predetermined cathode ray spot sizes and developing a plurality of predetermined deflecting frequencies, and thermionically selecting one of the predetermined frequencies and a spot size inversely proportional to the selected predetermined frequency.

6. A television receiver comprising a cathode ray tube, ray deflecting means, means for developing a cathode ray beam and focusing the said beam to a plurality of predetermined cathode ray spot sizes and means for generating a plurality of predetermined beam deflecting frequencies, and means for thermionically selecting one of the predetermined spot sizes and one of the predetermined deflecting frequencies in accordance with the received television signals.

7. A television receiver comprising a. cathode ray tube, ray deflecting means, means for developing a cathode ray beam and focusing the said beam to a plurality of predetermined cathode ray spot sizes and means for generating a plurality of predetermined beam deflecting frequencies, and means for thermionically selecting one of the predetermined frequencies and a spot size inversely proportional to the selected predetermined frequency.

8. A television receiver comprising a cathode ray tube, scanning means for deflecting a beam of electrons within the cathode ray tube at a plurality of predetermined frequencies, means to focus the beam of electrons to a plurality of different sizes, means to receive synchronizing signals, and resonant circuit and rectifier means for thermionically selecting one of the plurality of scanning frequencies and one of the plurality of spot sizes in accordance with the received synchronizing signals.

9. In a system for operating a television receiver including a cathode ray tube to reproduce television images upon the target area thereof in a predetermined fixed size viewing area so as to reproduce the pictures in difierent degrees of detail and at repetition rates related to the degree of detail selected and where the signals to represent the different degrees of detail and repetition rate are transmitted as signals'of different character the method steps which comprise receiving signals to control the television image reproduction, developing a cathode ray beam adapted to be focused to a plurality of difierent spot sizes and to be deflected at a plurality of different related deflection rates in accordance with desired detail of reproduced picture, supplying the received signals to the cathode ray tube to control the picture intensity and utilizing the received signals automatically to select one only of the plurality of the predetermined spot sizes and the predetermined deflection rates so that the produced picture area remains substantially constant with detail and repetition rate determined by the character of the received signal.

10. In a system for operating a television receiver including a cathode ray tube to; reproduce television images upon the target area thereof in a predetermined fixed size viewing area so as to reproduce thepictures in different degrees of detail and at repetition rates related to the degree of detail selected and where the signals to represent the different degrees of detail and repetition rate are transmitted as signals of different character the method steps which comprise receiving signals to control the television image reproduction, developing a cathode ray beam adapted to be focused to a plurality of different spot sizes and to be deflected at a plurality of different related deflection rates in accordance with desired detail of reproduced picture, supplying the received signals to the cathode ray tube to control the picture intensity and utilizing the received signals automatically and solely to select one only of the plurality of the predetermined spot sizes and the predetermined deflection rates so that the produced picture area remains substantially constant with detail andrepetition rate determined by the character of the received signal.

ceiver including a cathode ray tube to reproduce television images upon the target area thereof in a predetermined fixed size viewing area so as to reproduce the pictures in different degrees of detail and at repetition rates related to the degree of detail selected and where the signals to represent the different degrees of detail and repetition rate are transmitted as signals of different character which comprises means for receiving transmitted signals to control the television image reproduction, a cathode ray tube for converting the signals into electro-optical images by means of a cathode ray beam impacting upon a luminescent target area, means included within the cathode ray tube to focus the cathode ray beam to a plurality of different spot sizes and means to deflect the cathode ray beam relative to the target at a plurality of different deflection rates related to the desired detail in the electrooptical image to be reproduced and means for utilizing the received television signals automa ically to select one only of the plurality of predetermined scanning spot sizes and the predetermined deflection rates so that the target area scanned remains substantially constant and the detail and repetition rate are determined in accordance with the received signals.

ALFRED AUBYN LINSELL. 

